The present invention concerns a method and device for supplying weft yarn to the shed of a weaving machine.
As is known, it is possible in a weaving machine to supply the same type of weft yarn to the shed via different yarn feeders. Each yarn feeder hereby consists of at least one feed bobbin, a weft accumulator such as a prewinder, and insertion means to insert the weft yarn into the shed. It is clear that hereby the average amount of weft yarn supplied to the shed per unit of time equals the sum of the average amount of weft yarn taken from the respective feed bobbins being used per unit of time. As the weft yarn is unwound from a feed bobbin, this causes tensions in the weft yarn. It is known that when these tensions exceed a certain limit, the risk of the thread breaking is considerable.
Such tensions are caused among other things by the position of the feed bobbin in relation to the weft accumulator, the nature and geometry of the feed bobbin, the relation of the diameter of the feed bobbin to the distance between the feed bobbin and the next downstream thread guide, and the yarn extraction speed with which said weft yarn is unwound from the feed bobbin.
It is clear that with a given diameter of a given feed bobbin and a given distance between the feed bobbin and the next thread guide, the tension in the weft yarn depends on the yarn extraction speed. As a result, it is possible to determine the yarn extraction speed for each diameter of the feed bobbin at which said tension limit is exceeded, in other words at which the risk of the thread breaking is considerable.